Clinton's brutal win in South Carolina, and how delegates are allocated

Hillary Clinton today crushed Bernie Sanders in the South Carolina Democratic primary by a 74-26 margin, winning every South Carolina county. According to exit polls, black voters made up 61% of the Democratic electorate, and Clinton won by 86-14 with them; she also won white voters 54-46.

Since the Super Tuesday states will feature southern states, such as Alabama, Georgia and Tennessee, where blacks make up a large portion of the Democratic electorate, Clinton is very likely to have more big wins.

From Wednesday 11am Melbourne time, we will receive results from 12 states that will determine about one quarter of both parties' delegates. So how are these delegates allocated?

Republican delegate allocation

Both parties make use of Congressional Districts (CDs) for delegate allocation. CDs are used to elect members to the US House of Representatives in the same way members are elected to Australia’s House; there are 435 CDs with a minimum of one per state. California has the most CDs with 53.

The Republicans assign 13 delegates to each state, plus three for each CD. A large number of bonus delegates are awarded to states that voted Republican at the last Presidential election. States with Republican office holders, such as Senators and Governors, get one bonus delegate for each office holder.

The Republicans use a variety of methods to allocate delegates. Many states combine all their CD and statewide delegates, and award them either proportionally, or all delegates can go to the state’s popular vote winner. Other states use “winner takes all” by CD and statewide, in which the winner of each CD receives the three delegates for that CD, and the statewide winner gets all statewide delegates.

Other than South Carolina, all states that vote prior to the 14 March must use some form of proportional representation (PR). Many Super Tuesday states are using PR with both a lower and upper threshold. If a candidate wins more than 50% of the vote, that candidate wins all statewide delegates, and candidates must achieve at least 15% or 20%, depending on state, to win any statewide delegates. In the CDs, two delegates usually go to the winner, and one to the runner up, provided that the runner up gets at least 15% or 20%, and the winner is under 50%.

This link explains the rules for delegate allocation in the Super Tuesday states.

Trump could easily win a majority of all delegates in some states despite “proportional” allocation rules. If he wins all CDs in states such as Alabama and Georgia, he will win two of the three delegates for each CD. Statewide proportionality applies only to those candidates who pass the 20% threshold. Carson and Kasich are unlikely to pass that threshold in states that require it. If one of Cruz or Rubio also fail to pass the threshold, Trump will take well over 50% of statewide delegates; if both fail to pass it, he will take 100%.

Cruz’s home state of Texas, with 155 delegates, is the largest prize on Super Tuesday. It is likely that Cruz will win Texas, but Trump is well over the 20% threshold, and is likely to take some delegates.

The Republicans have a total of 2,472 delegates, so it takes 1,237 delegates to win the nomination. After the first four states, Trump leads with 82 delegates, followed by Cruz with 17, Rubio 16, Kasich 6 and Carson 4. Trump’s current huge lead is mainly because he won all 50 delegates in South Carolina, which was winner takes all by CD and statewide.

Democratic delegate allocation

Democrats allocate their delegates to states based on each state’s population, and how well Democratic Presidential candidates did in that state in the last three Presidential elections, relative to the national vote. States then divide their delegates into statewide and CD delegates. CDs that favour Democrats tend to receive more delegates.

Democrats award all delegates proportionally, provided candidates win over 15% of the vote in both CDs and statewide. In the Democrats' PR system, the cut-points are important; for a two-candidate race, the cut-points are half a delegate. For example, if a CD elects five delegates, when considering the vote won by only Clinton and Sanders, Clinton would need just over 50% (2.5 delegates) to win a 3-2 delegate split. She would need just over 70% (3.5 delegates) to win a 4-1 split.

Although candidates can be a little lucky or unlucky in the splits of individual CDs, the overall statewide delegate split will usually be roughly proportional to the statewide vote. If the race between Clinton and Sanders remains competitive, this proportional allocation means it will take until early June for one candidate to mathematically win a majority of all pledged delegates.

The Democrats have 712 superdelegates, which include all Democratic members of Congress (both House and Senate) and all Democratic governors; there are also a few Distinguished Party Leaders, such as former and current Presidents. All members of the Democratic National Committee are superdelegates. Unlike pledged delegates, superdelegates are free to choose who they will support, and the vast majority of those who have announced their choice are supporting Clinton; she currently leads superdelegates by 445-18.

Including superdelegates, there are a total of 4,763 Democratic delegates, so 2,383 delegates are needed to win the nomination. After the first four states, Clinton leads pledged delegates by 91-65. Sanders' big win in low-population New Hampshire had already been cancelled out by narrow wins for Clinton in higher population Nevada and Iowa, and she won the pledged delegate count in South Carolina 39-14.

The only Super Tuesday state where Sanders is crushing Clinton is his home state of Vermont, while she has huge leads in the southern Super Tuesday states. To make up for a likely southern state wipeout, Sanders needs to be winning big somewhere else, but outside Vermont, which has only one CD, there appear to be no states in the near future where he is dominating Clinton. If this holds up, Clinton should comfortably win the majority of the pledged delegates.